Our invention relates to curtain walls of buildings, and more specifically to a prefabricated curtain wall assembly composed of vertically alternating rows of window units and spandrel units for attachment to the floor structure of a building, in particular of a multistory building.
A prefabricated curtain wall in the form of an array of discrete window units and spandrel units is per se not new in the art. Japanese Laid Open Patent Application No. 56-28956 represents a typical conventional example of prefabricated curtain wall which is perhaps most pertinent to our invention. This prior art curtain wall comprises horizontal rows of spandrel unit attached respectively to the floor systems of a building, and horizontal rows of window units arranged alternately with the rows of spandrel units so as to enclose the open spaces between the floor systems. Each window unit is attached at its top end to one floor system and is coupled at its bottom end to an underlying spandrel unit.
We favor the division of a curtain wall into separate window units and spandrel units, rather than into units each integrally comprising a window subunit and a spandrel subunit, as the separate window units and spandrel units are smaller in size, ligther in weight, and so easier of transportation and assemblage. We do, however, object to the direct attachment of the top end of each window unit to a floor system in accordance with the noted prior art. The direct mounting of not only the spandrel units but also the window units to a floor structure has made their installation very troublesome as the window units must also have had their vertical positions correctly adjusted with respect to the floor structure at the time of their mounting. As an additional disadvantage, having being directly coupled to the floor structure at their top ends only, the window units have not been so strong against forces normal to their own plane as can be desired.
Another factor that merits consideration in designing curtain walls having both window units and spandrel units of different sizes is the cross sectional construction of the frame members of such units. The strength and rigidity of these frame members greatly affect the strength and rigidity of the complete curtain wall assembly. Frame members of the same cross sectional shape and size are normally employed for both window and spandrel units of different sizes. The frame members of larger size units are of course longer, and therefore less in rigidity, than those of smaller size units. Without reinforcements, the complete curtain wall would then materially lessen in rigidity and strength, particularly against forces normal to its plane.
An apparent solution to this problem might be the use of frame members of different cross sectional constructions for the curtain wall units of different sizes. This solution would be unpracticable, however, as the frame members of different cross sectional shapes or sizes would increase the manufacturing cost of the curtain wall units. Such different frame members would also require correspondingly different means for assembling the curtain wall units and mounting them to the floors of a building. The frame members of the different curtain wall units should therefore be made equal in cross sectional construction as far as possible. Separate reinforcement means may advantageously be employed where necessary.